Continuous Data Protection (CDP) allows a customer to roll back data to a previous point in time with fine granularity. This is superior to previous discrete data replication solutions because the recovery point can be fine-tuned to minimize data loss. CDP solutions are already available for block storage, files and databases. Although file systems and databases are the main users of block storage, a block CDP solution is also useful in any storage technology because it can recover all of the data storage in a data centre to a consistent state.
Critical data is often protected against disasters by mirroring it to another site. The remote copy can be updated synchronously with each write command issued by the application or asynchronously at a later time, according to the distance between sites.
Published US Patent Application No. US 2005/0251540, assigned to Atempra Technologies Inc., describes a data management system for data protection and disaster recovery. Disclosed therein is a special device driver in each host which captures data modifications and application-level events and saves them to a journal to ensure that data replicas have application-level consistency. The journal sits alongside the primary storage for the application, so there are two copies of the data on the primary site.
There remain the problems of inefficiencies of resource use in the need to provide special nonstandard device drivers in each host and in the need to provide duplicate storage facilities for storing the additional journal data.
It would thus be desirable to have a technological means for maintaining continuous data protection integrated with a remote copy facility, using commonly-available components and with minimal additional resource use.